First basin-wide experimental results on N-2 fixation in the open Mediterranean Sea

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Ibello V., Cantoni C., Cozzi S., Civitarese G.

GEOPHYSICAL RESEARCH LETTERS, vol.37, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 37
  • Publication Date: 2010
  • Doi Number: 10.1029/2009gl041635
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Middle East Technical University Affiliated: No


The Mediterranean Sea presents several biogeochemical anomalies compared to the global ocean. An unbalanced N budget, high nitrate/phosphate ratios in subsurface waters and low N-15/N-14 ratios in particulate and dissolved nitrogen suggest a significant occurrence of N-2 fixation. This study presents, for the first time, a basin-wide overview of direct measurements of N-2 fixation, with values in the North Atlantic for comparison, during late spring 2007. Very low N-2 fixation rates (0.052 +/- 0.031 nmols N l(-1) d(-1)) were observed in all sub-regions of the Mediterranean, in contrast to the higher values measured in the North Atlantic (0.300 +/- 0.115 nmols N l(-1) d(-1)). Higher phosphorus (inorganic or organic) concentrations were not associated with higher N-2 fixation rates. Low N-15/N-14 ratios in particulate organic nitrogen (from -2.10 to +4.11%), associated with low N-2 fixation rates, suggest that other N sources, such as atmospheric inputs, fuel the Mediterranean ecosystem. Citation: Ibello, V., C. Cantoni, S. Cozzi, and G. Civitarese (2010), First basin - wide experimental results on N-2 fixation in the open Mediterranean Sea, Geophys. Res. Lett., 37, L03608, doi: 10.1029/2009GL041635.